1. Field of the Invention
The present invention relates to a printer apparatus. Particularly, it relates to a laser beam printer apparatus.
2. Description of the Background Art
Printer apparatus that perform printing on a printing substrate such as a sheet of paper include laser beam printer apparatus. A laser beam printer apparatus performs printing by pressing a printing substrate upon a photosensitive drum on which toner has been placed in a predetermined geometry.
FIG. 18 illustrates a schematic cross section of a laser beam printer apparatus. The laser beam printer apparatus includes a housing 30 in which its various components are disposed. The laser beam printer apparatus includes a toner cartridge 25 containing toner, a photosensitive drum 11 for placing toner on a printing substrate in a desired geometry, and a transfer roller 12 for pressing the substrate onto photosensitive drum 11 with an appropriate pressing force. The printing substrate is shaped such that it can be moved along a transportation path 51.
The laser beam printer apparatus includes a rear door 1 disposed on the backside of housing 30. Rear door 1 is configured to be openable/closable as indicated by arrow 61. Transfer roller 12 is fixed to rear door 1. Closing rear door 1 causes photosensitive drum 11 to contact transfer roller 12 in a line. Further, transfer roller 12 is biased toward photosensitive drum 11 with a predetermined pressing force by a biasing means, not shown.
Preferably, transfer roller 12 is precisely arranged to be adjusted in its position relative to photosensitive drum 11 in order to place toner in a configuration to be printed. For example, the rotational axis of transfer roller 12 preferably is highly parallel with the rotational axis of photosensitive drum 11. Accordingly, the position of rear door 1 is preferably fixed such that it is not moved when rear door 1 is closed. For example, rear door 1, when closed, is preferably positioned precisely in the front/back direction and in the up/down direction of the laser beam printer apparatus.
To arrest an open/close member such as a door in a predetermined position, Japanese Patent Laying-Open No. 2004-132407, for example, discloses a hinge device for a mobile phone. The hinge device includes a slide piece having a linear recess and a cam member having a linear cam projection corresponding to the recess. The slide piece and the cam member are configured such that the recess and the projection oppose each other and are pressed against each other by a biasing means. The cam member is configured to be rotated with respect to the slide piece. In this mobile phone, the receiver part is fixed such that the cam projection is substantially parallel to the recess. Thus, when the cam projection of the cam member and the recess of the slide piece are aligned with each other in extension, the cam projection is fitted into the recess of the slide piece, and one of the housings of the hinge device is fixed.
Japanese Utility Model Laying-Open No. 4-90232 discloses an information device including an openable/closable display case. This information device provides a lock projection on one of its body cases and a lock recess on the other, which engages with the lock projection. It discloses the lock projection engaging the lock recess to prevent one of the display cases configured to be openable/closable from being disengaged. Particularly, it discloses the lock projection protruding in the direction of the rotational axis of the openable/closable display case to prevent the lock projection from being disengaged from the recess even when an external force is applied to the openable/closable display case to cause deformation.
In a laser beam printer apparatus illustrated in FIG. 18, it is preferable if transfer roller 12 is precisely positioned with respect to photosensitive drum 11 when rear door 1 is closed. That is, transfer roller 12 preferably is fixed such that it is not movable when rear door 1 is closed. If rear door 1 wobbles when rear door 1 is closed, toner cannot be placed in correct position on a printing substrate such as paper, for example the transfer roller shifts while toner is being placed which results in a disturbed transferred geometry. Thus, some printer apparatus may have an open/close door that is preferred to be precisely positioned when closed.
A hinge device disclosed in Japanese Patent Laying-Open No. 2004-132407 as above is suitable for a smaller device such as a mobile phone, however, it is not appropriate for a larger device such as an open/close door of a printer apparatus since a large force is applied to its rotational axis.
A lock projection such as in an information device disclosed in Japanese Utility Model Laying-Open No. 4-90232 is capable of fixing an open/close door in one direction related to the anchoring by the lock projection, however, it is not capable of fixing the open/close door in a direction perpendicular to the above one direction, such that the open/close door may be moved in a direction perpendicular to the one direction.